At 48VDC you could run 16AWG like 100ft and still be fine as long as the lights pull around 60W or less all together (which works out to ~12 lights on a circuit). And that circuit would only add another ~2W or so in power losses when energized.
That circuit is essentially what power over ethernet does today so you could replace romex with PoE Type 3/Type 4 plenum rated ethernet and it'd be like half the cost.
And if you really want to optimise for losses you could put the switches on the ethernet data line and use that for sensing rather than running the PoE circuit out to each light switch (and then de-energise the PoE circuit when the switches report off). Bonus points in that this would allow you to "reprogram" which light switch controls which circuit without needing to do any re-wiring.